Various types of downhole drilling tools including, but not limited to, rotary drill bits, reamers, core bits, and other downhole tools have been used to form wellbores in associated downhole formations. Examples of such rotary drill bits include, but are not limited to, fixed cutter drill bits, drag bits, polycrystalline diamond compact (PDC) drill bits, and matrix drill bits associated with forming oil and gas wells extending through one or more downhole formations. Fixed cutter drill bits such as PDC bits may include multiple blades that each include multiple cutting elements.
In typical drilling applications, a drill bit may be used in directional and horizontal drilling. Often in directional and horizontal drilling, the drill bit will drill vertically to a certain kickoff location where the drill bit will begin to curve into the formation, and at a certain point, the drill bit will begin horizontal drilling. One of the purposes of directional and horizontal drilling is to increase drainage of a reservoir into the wellbore and increase production from a well.
When drilling vertical wellbores, the drill string and various other items located above the drill bit supply the desired force on the bit, usually referred to as the weight on bit (WOB). The WOB enables the bit to adequately engage the formation with a sufficient rate of penetration (ROP) and depth of cut. However, as the wellbore begins to change from vertical to horizontal, the drill string is held against the lower wall of the wellbore by gravity. Under these conditions, the portion of the drill string in the kickoff and horizontal portions of the wellbore may not exert any weight on the bit because the drill string weight is exerted against the lower wall of the wellbore. This leads to very small WOB and a low ROP. Thus, in directional and horizontal drilling, any force used to turn the drill bit must overcome the friction between the drill string and the lower wall of the wellbore. Additionally, the torque required to turn the drill bit in some directional and horizontal drilling is supplied only by a downhole motor and is therefore very limited. This limited torque may lead to “motor stall” if the instant depth of cut of the drill bit is so high that the combination of torque and revolutions per minute (RPM) produced by the motor is not sufficient to effectively rotate the drill bit.